In general, trace elements are mainly checked for calcium, iron, zinc, copper, magnesium, and blood lead. Since trace elements play an important role for babies, too high or low can affect the health of babies. Most babies less than six months old have enough trace elements in breast milk or formula, and babies older than six months old will not be deficient if they are fed with nutritious supplements. For children, these tests can reflect the real problem, but sometimes a normal result does not mean that the child is not deficient in trace elements. Doctors need to make a comprehensive assessment in conjunction with the child’s clinical symptoms, daily diet and growth and development, and not just rely on the value on the test report to determine whether the child has a trace element deficiency. Trace element testing is generally used in certain special cases to provide clinicians with a reference for diagnosis, and the results can only be used as an auxiliary reference.